Ribaliterally means 'to grow; to
increase.' Technically, it denotes the amount that a lender receives from a
borrower at a fixed rate in excess of the principal. It is of two kinds:
1. RibaNasi'a - taking
interest on loaned money.
2. RibaFadal - taking
something of superior quality in exchange for giving less of the same kind of
thing of poorer quality.

In English it is usually translated as “Interest” or “Usury”

2. Prohibition in Islam:

The word “Riba” is
used in the Holy Quran 8 times. In 30:39,4:161,3:130,
2:276,2:278 and 3 times in 2:275. The Quran says

“Those who devour usury will not stand
except as stand one whom the Evil one by his touch Hath
driven to madness. That is because they
say: "Trade is like usury," but Allah hath permitted trade and
forbidden usury. Those who after receiving direction from their Lord,
desist, shall be pardoned for the past; their case is for Allah (to judge); but
those who repeat (The offence) are companions of the Fire: They will abide
therein (for ever).” (Quran 2:275)

“O ye who believe!Devour not usury, doubled and
multiplied; but fear Allah. that ye may (really)
prosper.” (Quran 3:130)

“O ye who believe!Fear Allah, and give up what remains of
your demand for usury, if ye are indeed believers. If ye do it not, Take notice of war from Allah and His Messenger. But if ye
turn back, ye shall have your capital sums: Deal not unjustly, and ye shall not
be dealt with unjustly.”(Quran 2:278-279)

If you are dealing in interest. Please do not expect angels to come down
with swords to wage a war against you. It is talking about the severity of the
sin. For other sins like alcohol, gambling etc. the Quran
says

“O ye who believe!
Intoxicants and gambling, (dedication of) stones, and (divination by) arrows,
are an abomination,- of Satan's handwork: eschew such
(abomination), that ye may prosper.” (Quran 5:90)

Here the Quran says that intoxicants and
gambling are Satan’s handiwork and abstain from it. In the case of Riba(Interest) the Quran
does not only say that it’s a sin but it says that Allah (SWT) and his
messenger Muhammad (pbuh) will wage a war against.
Showing how grave this sin really is. Prophet Muhammad (pbuh)
said :

Prophet Muhammad (pbuh)
classified it among the seven major sins

"Volume 8, Book 82, Number 840:

Narrated
Abu Huraira:

The Prophet said,
"Avoid the seven great destructive sins." They (the people!) asked,
"O Allah's Apostle! What are they?" He said, "To join partners
in worship with Allah; to practice
sorcery; to kill the life which Allah has forbidden except for a just
cause (according to Islamic law); to
eat up usury (Riba), to eat up the property
of an orphan; to give one's back to the enemy and freeing from the battle-field
at the time of fighting and to accuse chaste women who never even think of
anything touching chastity and are good believers."

Some Muslims may argue that only the taking
of interest is prohibited. But one SahihHadith says

“·HazratJabirr.a. has reported that the Messenger of Allah cursed the devourer of
usury, its payer, its scribe and its two witnesses. He also said that they were
equal (in sin).” (Mishkat-ul-Masabih)

Though there are many hadith
which condemn riba (interest) but these two are
sufficient for now.

3. Prohibition in the Bible

“Do not
charge your brother interest, whether on money or food or anything else that
may earn interest.”
(Deuteronomy 23:19)

“Do not
take interest of any kindfrom him, but fear your
God, so that your countryman may continue to live among you.”
(Leviticus 25:36)

“If you
lend money to one of my people among you who is needy, do not be like a moneylender;
charge him no interest”
(Exodus 22:25)

Righteous
servant of God doesn’t take interest

5"Suppose there is a righteous man who does what is just and
right.

6 He does not eat at the
mountain shrines or look to the idols of the house of Israel. He does not defile his
neighbor's wife or lie with a woman during her period.

7 He does not oppress
anyone, but returns what he took in pledge for a loan. He does not commit
robbery but gives his food to the hungry and provides clothing for the naked.

8He does not lend at usury or take excessive interest. He
withholds his hand from doing wrong and judges fairly between man and man.

“10"Suppose
he has a violent son, who sheds blood or does any of these other things

11 (though the
father has done none of them): "He eats at the mountain shrines. He
defiles his neighbor's wife.

12 He oppresses the poor and needy. He commits robbery. He
does not return what he took in pledge. He looks to the idols. He does
detestable things.

13 He lends at
usury and takes excessive interest.
Will such a man live? He will not! Because he has done all these detestable
things, he will surely be put to death and his blood will be on his own head” (Ezekiel 18:10-13)

Jesus
Christ (pbuh) came to fulfill the Law. He said:

“[17] Think not
that I am come to destroy the law, or the prophets: I am not come to destroy,
but to fulfil.[18]
For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be
fulfilled.[19]Whosoever
therefore shall break one of these least commandments, and shall teach men so,
he shall be called the least in the kingdom of heaven: but whosoever
shall do and teach them, the same shall be called great in the kingdom of
heaven.
[20] For I say unto you, That except your righteousness shall exceed the
righteousness of the scribes and Pharisees, ye shall in no case enter into the
kingdom of heaven.” (Mathew 5:17-20)

The Hebrew
word used for interest/usury in all these verses is

neh'-shek: which means:

From H5391; interest on a debt: -
usury.

Hence, TheQuran and Bible both consider
interest to be a sin and Muslims, Christians and Jews Should NOT indulge in it.